Yukichi Fukuzawa is a tall man with long silver hair, metallic blue eyes, and a face set in permanent sternness. He favors traditional Japanese attire: a green yukata beneath a black haori featuring golden zigzag borders, completed by zori sandals and white tabi socks. In his youth, martial arts training saw him clad in a black hakama, kimono, and keikogi.
Born in Yokohama, Fukuzawa trained at a government martial arts school, forging a potent blend of friendship and rivalry with Ōchi Fukuchi. During the Great War, he operated as a government assassin codenamed "Silver Wolf," eliminating war-hawk bureaucrats and foreign military leaders. He abandoned this path upon realizing he'd begun to relish killing, an act that led to societal ostracization. He later gained notoriety as a supremely competent lone-wolf bodyguard.
His trajectory shifted during a theater murder investigation where he encountered 14-year-old Ranpo Edogawa. Recognizing Ranpo's exceptional deductive skills and social difficulties, Fukuzawa took him under his wing, framing Ranpo's talent as a supernatural ability to instill purpose. This mentorship deepened into a father-son bond. To harness Ranpo's gift and create an organization of "strong yet kind" ability users dedicated to Yokohama's peace, Fukuzawa enlisted government-connected Sōseki Natsume's aid to establish the Armed Detective Agency (ADA), operating under the government-granted Ability Business Permit.
Fukuzawa possesses the ability "All Men Are Equal," which suppresses and stabilizes the powers of ADA members who pass an entrance exam proving their commitment to saving lives. This ability awakened with his newfound confidence in leadership after founding the ADA. A master martial artist and swordsman, once counted among the "Goken" (Japan's five greatest swordsmen), he demonstrates exceptional combat prowess, mastering techniques like *kote gaeshi*, *seoi nage*, iaido, *shukuchi*, and *muto dori*, evident in battles against assassin groups and rivals like Ōgai Mori.
As ADA president, Fukuzawa prioritizes his subordinates' safety and Yokohama's stability above all else. He enforces strict discipline but exhibits profound care, such as halting all operations to rescue abducted members like Atsushi Nakajima. He co-founded the Tripartite Framework with Natsume and Mori to maintain the city's balance. Despite his stoic exterior, he harbors a soft spot for cute things: he instantly hired Kyōka Izumi after she made a "cute face" and keeps cat treats in his sleeves. His personality blends unwavering principle with dry humor, as when he told criminals threatening Mori to "have fun" attempting the task.
Fukuzawa's development centers on his transition from solitary assassin to protective leader. Key events include recruiting Kenji Miyazawa after discovering his flood-prevention feat, temporarily allying with Mori to protect Yokohama, and confronting Fukuchi during the Decay of the Angel crisis. His leadership philosophy emphasizes equality and compassion, offering orphaned or marginalized individuals like Atsushi, Kyōka, and Ranpo a place to belong.
Elements of Fukuzawa's past occasionally resurface, notably his unresolved conflict with Fukuchi over their wartime choices. His commitment to justice remains absolute, even when afflicted by ability-suppressing viruses like "Cannibalism," where he ordered the ADA not to defend him to preserve citywide peace. His character embodies the ideals of his ability's namesake—equality achieved through disciplined guidance and unwavering resolve.